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    <script>
        /* 
             九九乘法表:双重for循环

             *
             **
             ***
             ****

             i    num(j 的最大值)
             0     1
             1     2
             2     3
             
             i + 1 = num
        */
        /* let num = prompt('请输入行数');
        for (let i = 1; i <= num; i++) {
            let star = '';
            for (let j = 1; j <= i; j++) {
                star = star + (i + '*' + j + '=' + i * j) + '   ';
            }
            console.log(star);
        } */
        /*     let num = prompt('请输入行数');
            for (let i = num; i > 0; i--) {
                let star = '';
                for (let j = 1; j <= i; j++) {
                    star = star + (i + '*' + j + '=' + i * j) + '   ';
                }
                console.log(star);
            } */
        /*  let num = prompt('请输入行数');
         for (let i = 1; i <= num; i++) {
             let star = '';
             for (let j = 1; j <= i; j++) {
                 star = star + i + '*' + j + '=' + (i * j) + ' ';
             }
             console.log(star);
         } */
         for(let i = 1; i <= 9; i++){
            let space='';
            let star = '';
               for(let j = 1; j <= 9; j++){
                    if(j<i){
                        space = '';
                    }else{
                        star = star + i + '*' + j + '=' + (i * j) + '     ';
                    }

               }
               console.log(star);
         }
    </script>
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